Automatic braking mechanism

ABSTRACT

Braking mechanism for a traction apparatus of the opposed traction unit type, automatically operable independent of the pneumatic control for the service brakes and operated by means of an air cylinder through the same pneumatic pressure source used for the chain drive of each traction unit. The braking mechanism includes a pivotally-mounted brake arm having sprocket teeth engaging means thereon movable into and out of engagement with the sprocket teeth of each chain drive sprocket wheel by means of a toggle linkage which, when collapsed by the air cylinder, moves the brake arm out of engagement and, when moved slightly past a dead-center position by the air cylinder, moves the brake arm into engagement under the assistance of a torsion spring.

United States Patent Buress, III 1 1 Dec. 5, 1972 [54] AUTOMATIC BRAKINGMECHANISM FOREIGN PATENTS OR APPLICATIONS [72] Inventor: John W. Buress,III, Winston- 650,990 10/1928 France ..188/31 Salem, NC. 84,061 8/1935Sweden ..l88/170 [73] Assignee: Drill Carrier Corporation, Salem,Primary Examiner Benjamin Hersh Assistant Examiner-Leslie J. Paperner[22] Filed: May 17, 1971 Attorney-Watson, Cole, Grindle & Watson Brakingmechanism for a traction apparatus of the op- U-S- Clposed traction typeautomatically operable inde- 188/170, 192/ 305/9 pendent of thepneumatic control for the service [51] Int. Cl. ..B62d 11/04, Fl6d 65/24brakes and operated by means of an air cylinder [58] Field of Search...l80/6.48; 188/31, 60, 69, 170; through the same pneumatic pressuresource used for 305/9; l92/3R; 74/411.5 the chain drive of each tractionunit. The braking mechanism includes a pivotally-mounted brake arm [56]R f ren Cit d having sprocket teeth engaging means thereon movable intoand out of engagement with the sprocket UNITED STATES PATENTS teeth ofeach chain drive sprocket wheel by means of 2,994,393 8/1961 Whaley..180/6.48 a f linkage which when collapsed by the air 3,371,735 3/1968Masera ..3o5 9 x cylmder brake arm of f 'l 2,295 196 9/1942 Barr..l88/l70 when. moYed Slightly past a l posmon by the air cylmder, movesthe brake arm mto engagement 3,580,345 5/1971 Brown ..305/9 X under theassistance of a torsion Spring 2,796,301 6/1957 Lear et a1. ..305/92,860,731 11/1958 Hause ..l88/69 6 Claims, 2 Drawing Figures PNEUMATICPRESSURE SOURCE PAIENTEDnEc 51972 3.704.757

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ATIOK/VEYS AUTOMATIC BRAKING MECHANISM This invention relates generallyto traction apparatus of the opposed traction unit type and moreparticularly to anautomatic braking mechanism for such apparatus whichserves to brake each traction unit through the same pneumatic pressuresource used for the chain drive of each traction unit.

In the known traction apparatus each traction unit is provided with abraking and clutching arrangement by pneumatic action for controllingthe steering operation of the apparatus. The brakes may, of course, beapplied when the apparatus is at rest or at an incline but, if leftstanding for any significant length of time, a leak in the pneumaticcontrol line may cause the brakes to release.

It is therefore an object of the present invention to provide 'a brakingmechanism which is operable automatically, is independent of thepneumatic controls for the service brakes and is operated from the samepneumatic power source which controls operation of the pneumatic motorwhich drives each chain of the opposed traction unit.

Another object of the present invention is to provide such a mechanismwherein an air cylinder and piston unit is operable through the chaindrive air source to effect a braking action of one of the sprocketwheels of the traction units in such a manner that the brake is therebyretracted when the drive motors are actuated to drive the traction unitand the brake is applied when the drive motors are not actuated.

A further object of the present invention is to provide such a brakingmechanism including braking arm means which are moved by the aircylinder and piston unit into and out of braking engagement with the onesprocket wheel by means of a toggle link mechanism which, when movedslightly off of a dead-center position during retraction of the pistonof such unit in the absence of pressure from the pneumatic pressuresource, the braking arm means is caused to move into braking engagementwith the one sprocket wheel; conversely, full collapse of the togglelink mechanism during extension of the piston of such unit controlled bythe air pressure from the pneumatic pressure source, causes the brakearm means to be moved out of braking engagement with the one sprocketwheel.

A still further object of this invention is to provide such a brakingmechanism wherein a torsion spring is provided for assisting in theretraction of the piston within the unit, the off dead-centerdisposition of the toggle mechanism assuring continued brakingengagement even in the event of torsion spring failure.

A still further object of the present invention is to provide such abraking mechanism wherein the brake arm means is provided with sprocketengaging means for interrneshing with the teeth of the one sprocketwheel to thereby positively prevent any movement thereof.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawingswherein:

FIG. 1 is a side elevational view of the braking mechanism in accordancewith the present invention for one of the partially shown tractionunits; and

FIG. 2 is an elevational view of the braking mechanism taken along theline 2-2 of FIG. 1.

Turning now to the drawings wherein like reference characters refer tolike and corresponding parts throughout the several views there is showna portion of a frame 10 of a traction apparatus in conjunction withother elements of such apparatus as is necessary to adequately describethe present invention. Only one of a pair of traction units such as 11is shown along with its accompanying drive control means in order to simplify the disclosure.

Each traction unit is mounted in some conventional manner to the frame10 with its axle 12 having at one end an idler sprocket wheel 13. An airdriven motor means 14 is also mounted on the frame for pneumaticallydriving a drive sprocket wheel 15 with such drive motion beingtransmitted to the idler sprocket wheel by the conventional means of achain 16 extending about each sprocket wheel. A pneumatic pressuresource, shown schematically in FIG. 1, is provided for supplying airpressure through air line 17 to the air motor 14 which, in conjunctionwith well-recognized brake and clutch connections, operate each tractionunit to propel and steer same. Valving V, also s shown schematically inPK]. 1, is provided along air line 17 for controlling the air supply todrive motor 14 inthe normal manner.

The braking mechanism, referred to generally by reference numeral 18, iscontrolled through air line 17 from the same pneumatic pressure sourceand valving which controls the air supply for the drive motor. It willbe seen that the braking mechanism 18 is designed in such a manner thatwhen the valving V is actuated to supply the drive motor 14 with air thebraking mechanism is likewise operated so as to release the brakingaction thereof during movement of each traction unit. Conversely, whenthe air supply through valving V is cut off for the drive motors it islikewise automatically cut off for the braking mechanism so that abraking action is effected until it is once again released through theair supply which simultaneously controls the motor drive.

The braking mechanism 18 is actuated by means of its air cylinder andpiston unit 19 which is secured at one end as at 21 to the frame 10 andwhich has a piston rod 22 extending outwardly therefrom. The cylinderunit is operably connected with the pressure source and valving throughair line 17. A piston rod and adapter 23, in the form of a yoke whichhas a pin 24 extending transversely through its two arms as most clearlyshown at FlG. 2, is provided at the free end of piston rod 22. A togglelink mechanism is supported by transverse pin 24 by means of which abrake arm assembly 25 is made to move into and out of braking engagementwith sprocket wheel 13. This toggle mechanism comprises link members 26pivotally secured at one end to transverse pin 24 and at their oppositeends pivotally to brake arm assembly 25 through a pin member 27. Thetoggle linkage mechanism further includes a link member 28 pivotallysecured at one end to pin 24 while at its opposite end is pivotallysecured to a pin member I 29. This pin member 29 is fixedly secured atone end to the frame 10 through a base plate 31 by means of threadedfasteners 32. The free end of pin 29 has a torsion plate 33 fixedthereon, as by threaded screw member 34, and held against rotation bymeans of a key pin 35. Between the torsion plate 33 and the link member28 a torsion spring 36 is provided and freely stantially identical arms39 pivotally secured at one end to frame about a pivot pin 41 with thetransverse pin 27 also extending therethrough between its ends, spacers42 being provided for the link members 26. The arms 29 are spaced aparta distance greater than the thickness of sprocket wheel 13 and, at thefree ends of the arms, sprocket engaging means is provided in the formof elongated rollers 43 rotatably secured between arms 39 and being ofsuch a diameter approximately equal to the grooved diameter of eachsprocket wheel tooth of sprocket 13.

Also, it should be noted that base plate 31 may be adjusted toward andaway from sprocket wheel 13 for adjusting the entire braking mechanism18 if it is desired to increase or decrease the intermeshing engagementbetween rollers '43 and the teeth of wheel 13. Such an adjustment issimply effected by means of an allen screw 46 located within adjustmentblock 45, one end of the screw bearing against plate 31. Fasteners 32extend through elongated bores 44 to accommodate movement of the platetoward and away from wheel 13.

The operation of the breaking mechanism will now be described. Brakingaction between the arm assembly 25 and the sprocket wheel 13, shown insolid lines in FIG. 1, is effected through the air control by valving Vand piston unit 19 automatically retracts for lack of air pressurewithin this unit. Retraction by the piston rod is enhanced by means oftorsion spring 36 which releases its built up torsional force afterhaving been uncoiled during brake release as will be explainedhereinafter. During retraction the toggle linkage is urged into anextended and nearly substantially aligned position of the links butslightly past a dead-center position so as to cause a spontaneouslocking of the links in their extended condition in which condition thebrake is urged into operative engagement with the sprocket 13 as shownin full lines in FIG. 1. By reason of this over dead-center relationshipof the toggle linkage, the brake will remain applied even in event offailure of the coil spring 36. In other words, this is a fail safefeature such that unless the driving motor is actuated to drive theendless track, the brake is effectively applied and will be maintainedapplied. The rollers 43 of the brake arm assembly 25 are convenientlyadapted for meshing engagement with the sprocket teeth and, because ofthe cooperating conformation of the sprocket teeth themselves, it can beseen that even though the rollers when initially engaged may strike theends of the sprocket teeth, only a slight rolling or movement of thesprocket is required in either direction to firmly engage the rollerswith the teeth.

when, on the other hand, the driving motor 14 is actuated and air issimultaneously admitted to the air cylinder and piston unit 19, thepiston rod 22 is extended so that the knee of the toggle linkage isbroken and is urged to the position shown in broken lines in FIG. 1thereby positively retracting the free end of the brake arm assembly 25from braking engagement with the sprocket 13. In this condition, torsionspring 36 is slightly wound-up on the member 29.

From the foregoing, it can be seen that a simple yet highly effectivebraking mechanism has been devised for effectively braking the tractionunits automatically upon discontinuance of the air pressure for the airmotor driving means for such traction units. The present mechanism isnot only fail safe and locked in place during braking engagement withthe sprocket wheel, but is absolutely independent of the service brakingsystem and easy to manufacture and install on existing tractionapparatus as well as being economical and simple in its design.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is, therefore, to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

What is claimed is:

1. In a traction apparatus having a frame, opposed traction unitsmounted on said frame, a driving connection for each said unitcomprising pairs of spaced sprocket wheels on said frame and an endlesschain extending about each said wheel pair, pneumatically operated meansfor driving each of said wheel pairs, a pneumatic pressure source andvalving for regulating the pneumatic pressure, a braking mechanism onsaid frame for each said unit including movable means for braking one ofsaid sprocket wheels, each said mechanism being pneumaticallyinterconnected with each said valved pneumatic pressure source, eachsaid mechanism also including an air cylinder piston unit connected withsaid movable means and operable through said source to retract saidpiston to thereby actuate said movable means into braking engagementwith said one sprocket wheel when the pneumatic pressure isdiscontinued, and to extend said piston to thereby actuate said movablemeans out of braking engagement with said one sprocket wheel when thepneumatic pressure is valved on, whereby said one sprocket wheel isbraked only during inoperation of the driving means, said piston unitbeing connected with said movable means by a toggle linkage comprisingtwo link member sets each pivotally connected at one end to the pistonrod of said unit thereby defining a toggle knee, and pivotally connectedat their other ends, respectively, to said movable means and to saidframe, the toggle knee during full retraction of said piston rod lyingslightly out of alignment with said link member other ends therebydefining an off-dead-center arrangement of said link members whereby anytendency for accidental release of the brake is substantially avoided.

2. In the traction apparatus according to claim 1 wherein the pivotalconnection between said link member other end and said frame includes apivot pin member fixedly secured at one end to said frame, a disk membersecured to the other of said pin member, and a torsion spring disposedin a piston retracting position about said pin member, opposite ends ofsaid spring being secured respectively to said disk member and to saidlink member which is pivotally connected to said pin, said torsionspring thereby assuring a full retraction of said piston within saidcylinder and piston unit during the locking engagement of saidmechanism.

3. In the apparatus according to claim 4 wherein said pivot pin memberis secured to said frame through a base plate having bores thereinslightly elongated in a direction towards said arm members, securingmeans extending through said elongated apertures, and adjustment meanson said frame near said base plate for adjusting said base plate andtherefore said arm members toward said one sprocket wheel.

4. In the traction apparatus according to claim 1 wherein said movablemember comprises a braking arm means pivotally secured at one end tosaid frame and having sprocket teeth engaging means at its free endwhereby said one sprocket wheel is braked as said teeth engaging meansintermesh with the teeth of said one sprocket wheel driving extension ofsaid piston rod causing collapse of said link member sets at said knee.

5. In the traction apparatus according to claim 5 wherein said brakingarm means comprise a pair of parallel arm members spaced apart adistance greater than the thickness of said one sprocket wheel wherebysaid arm members are disposed on opposite sides of said endless chain.

6. In the apparatus according to claim 5 wherein said sprocket teethengaging means comprises a plurality of elongated rollers disposed inparallel relationship with the axis of said one sprocket wheel.

1. In a traction apparatus having a frame, opposed traction unitsmounted on said frame, a driving connection for each said unitcomprising pairs of spaced sprocket wheels on said frame and an endlesschain extending about each said wheel pair, pneumatically operated meansfor driving each of said wheel pairs, a pneumatic pressure source andvalving for regulating the pneumatic pressure, a braking mechanism onsaid frame for each said unit including movable means for braking one ofsaid sprocket wheels, each said mechanism being pneumaticallyinterconnected with each said valved pneumatic pressure source, eachsaid mechanism also including an air cylinder piston unit connected withsaid movable means and operable through said source to retract saidpiston to thereby actuate said movable means into braking engagementwith said one sprocket wheel when the pneumatic pressure isdiscontinued, and to extend said piston to thereby actuate said movablemeans out of braking engagement with said one sprocket wheel when thepneumatic pressure is valved on, whereby said one sprocket wheel isbraked only during inoperation of the driving means, said piston unitbeing connected with said movable means by a toggle linkage comprisingtwo link member sets each pivotally connected at one end to the pistonrod of said unit thereby defining a toggle knee, and pivotally connectedat their other ends, respectively, to said movable means and to saidframe, the toggle knee during full retraction of said piston rod lyingslightly out of alignment with said link member other ends therebydefining an off-deadcenter arrangement of said link members whereby anytendency for accidental release of the brake is substantially avoided.2. In the traction apparatus according to claim 1 wherein the pivotalconnection between said link member other end and said frame includes apivot pin member fixedly secured at one end to said frame, a disk membersecured to the other of said pin member, and a torsion spring disposedin a piston retracting position about said pin member, opposite ends ofsaid spring being secured respectively to said disk member and to saidlink member which is pivotally connected to said pin, said torsionspring thereby assuring a full retraction of said piston within saidcylinder and piston unit during the locking engagement of saidmechanism.
 3. In the apparatus according to claim 4 wherein said pivotpin member is secured to said frame through a base plate having borestherein slightly elongated in a direction towards said arm members,securing means extending through said elongated apertures, andadjustment means on said frame near said base plate for adjusting saidbase plate and therefore said arm members toward said one sprocketwheel.
 4. In the traction apparatus according to claim 1 wherein saidmovable member comprises a braking arm means pivotally secured at oneend to said frame and having sprocket teeth engaging means at its freeend whereby said one sprocket wheel is braked as said teeth engagingmeans intermesh with the teeth of said one sprocket wheel drivingextension of said piston rod causing collapse of said link member setsat said knee.
 5. In the traction apparatus according to claim 5 whereinsaid braking arm means comprise a pair of parallel arm members spacedapart a distance greater than the thickness of said one sprocket wheelwhereby said arm members are disposed on opposite sides of said endlesschain.
 6. In the apparatus according to claim 5 wherein said sprocketteeth engaging means comprises a plurality of elongated rollers disposedin parallel relationship with the axis of said one sprocket wheel.